Comtech EF Data CRS-300 - Manual (Page 192)

CRS-300 1:10 Redundancy Switch MN/CRS300.IOM
Modem, RMI/TMI, and Switch Configuration Revision 19
5–28
5.6.2.5 Set the Backup Holdoff Period
If a Traffic Modem fails, the Switch waits for the backup holdoff time to determine two things:
1) Does the Traffic Modem remain faulted?
and
2) Is the Redundant Modem not exhibiting the same fault?
If the answer is yes to both questions for the entire backup holdoff time, then the Switch first
bridges the faulted modem with the Redundant Modem. If the fault is sustained, then the
switchover to the Redundant Modem is completed and the Redundant Modem carries the
traffic.
There will be no switchover if the Redundant Modem is faulted. Make sure that the Holdoff
times are long enough (default = 10 seconds) for the Redundant Modem to be configured and to
lock onto the signal.
Use the CRS-300 Front Panel menu to set the Backup Holdoff Period. Do these steps:
Step Task
1 Use the [←][→] keys to select the nested CONFIG: OPTIONS  HOLDOFFS menu.
2 Change the BACKUP HOLDOFF to any number from 1 to 99 seconds.
5.6.2.5.1 Set the Restore Holdoff Period
The "Restore Holdoff" setting, which is also programmable from 1 to 99 seconds, determines
the Switch's ability to automatically put a backed-up Traffic Modem online again if its fault
clears.
Normally, a failed modem that is taken offline remains offline indefinitely. If the fault clears,
traffic is returned to the unit (in AUTO mode) only if another Traffic Modem then fails.
If the fault on the originally failed modem has been clear for the full programmed Restore
Holdoff time, the Switch places that modem back online and bridges the newly faulted modem.
If the new fault is sustained, the Redundant Modem can then be used to back up the newly
faulted modem.
If you do not enable the Priority selection (see Sect. 6.2.2.3.1 CONFIG: OPTIONS PRIORITY),
then the Switch deals with Traffic Modem failures on a "first come, first serve" basis. If you set
the Switch to bridge the highest priority circuit, this will minimize switching time in the event of
a failure. If two faults occur simultaneously and are both sustained for the holdoff time, then the
Switch will back up the lower-numbered circuit.
If the CDM-Qx/QxL configuration includes Carrier-in-Carrier  this holdoff time should
be no less than 8 seconds.